If money is key you can travel on a Zone 1-6 travelcard. This is valid on bus route 81 from Slough to Hounslow where you can pick up the tube. This ticket is £8.50 for the off-peak version, valid after 0930 and is not valid on any other transport in Slough. Expect the journey to take 2 hours or more each way. You should be able to buy the ticket at Slough Station even though it is not valid on any trains from there.